Alternating current controlled power transmission



May 18, 1948. L. A. TROFIMOV 6 ALTBRNATING CURRENT CONTROLLED POWER TRANSIISSION Filed Dec. 5, 1944 2 Sheets-Sheet 1 INVENTOR. LBV 7;0/1 177 o y HTToR/VEY 4 L. A. TROFIMOV I 2,441,606

ALTERNATING CURRENT CONTROLLED POWER TRANSMISSION Filed Doc. 5, 1944 2 Sheets-Sheet 2 IN V EN TOR.

BY Lev H 7:0/7/77OV HTTOR/VEY Patented 18, 1948 UNITED STATES PATENT OFFICE ALTIINA'I'ING CURRENT O0 N'I'ROLLED rowsa rasnsmssrox m a. Troiimov, Wiilouhbr. om

minim mm 5, 1944, Serial No. seam 14 Claims. (01. ua-m This invention relates to power transmissions of the general class in which the power of a continuously running motor is transmitted to a load, or to a load driving element, to drive it at variable speed, irom rest or zero speed to a maximum speed, by controlling the transmission itself as distinguished from controlling the power supplying motor.

The power supplying motor may therefore be any kind of a motor, electric D. (2.; or electric A. C.; or internal combustion, etc., etc., with the advantage that the motor can always run at an emcient speed regardless of the speed of the load, or of the load driving element. I

The transmission may be constructed-in various torms or types, and may be controlled by various means, but the form, or forms of the transmission and particularly the controls thereof to which, the present disclosure is directed, comprises, among other things: 1." difl'erential gearing the-piniom-carr'yin'g spider oi whichis drivenby the power supplying motor; a flrst' and a second diiierential geariboth' meshed with the spider-carried-pinions; theifirst differential gear being connectedj'toaload driving" 'element;. the second-diil'erential" gear being connected to anfalternating current" induction generator, the

electrical generated load of whichis varied .by varying the potential applied toits .iield winding, through the agency of aninduction apparatus, or transformer, or the like; and the variations oi electrical load exerting a retarding or braking 2 To provide an improved power transmission 01' the diflerential gearing class, and in which the transmitted or output power is controlled by controlling, the electrical load of an alternating current type induction generator driven by the transmission;

' nating current mains. e

Other objects will be apparentto those skilled in' the art to which my invention appertains.

The invention is fully disclosed in the following description taken in connection with the accompanying drawing, in which:

Fig. 1 is a diagrammatic view 0! an embodiment of the invention, in which the" transmis- -sion comprises a double diflerential gearing, and

iormer; v

Fig. 1A is a fragmentary view of a part of Fig. 1

action on the second diflerential gear and controlling the torque and speedot the load driving" element. f A transmission and contr'joi'oithis general type in which a single diflerential gearing is u tilized,

is shown .and described in: my copendingappl'ication Serial No. 460,511, died October 2, 1942;

and atransmiss'ion and control of this general type in' which a double diirerential gearing is utilized is shown-and described in my copending application Serial No. 453,810, flied August 6, 1942, now Patent No. 2,365,982; and the subject matter of the present disclosure which illustrates and describes both forms is divisional therefrom respectively, and is also in part a continuation thereof It is among the objects of the invention:

To provide generally an improved motor driven power transmission;

two. induction generators, each oi which has a i g e ase wind a'jenersized through a transillustrating additional gears which in some cases may be desirable;

Fig. 2 is a viewsimilar to Fig. 1, but with parts omitted for simplicity and in which the induction generators have three phase windings;

Figs. 3 and 4 are views similar respectively to Figs. 1 and 2, but in which the transmission utilizes a single differential gearing and a single generator;

for the triplicate transformers 01' Fig. 4 or of 1 Fig. 2.

Referring to Fig. 1 of the drawing. I have shown at i and 2 a pair oi differential gearings.

The gearing i comprises a spider element 3 rotatably supporting pinions H with which are mesh d dlflerential gears I and I. The differen- 3 tial gearing 2 comprises a spider element 1 rotatably supporting pinions 8-4 with which are meshed differential gears and The bearings for the gears are not shown, the view being diagrammatic. but it will be understood by those skilled in the art that the spider elements and the differential gears are rotatably supported.

A power supplying motor is diagrammatically shown at H and itdrives a pinion H which supplies power to drive both spider elements and I, and this may conveniently be done by providing gear teeth and II respectively on peripheral portions of the spider elements I and and by meshing the two spider elements together as at ll: whereby the motor II will drive the spider elements in opposite directions of rotation.

of teeth, and that the differential gears I, I,

and Ill be alike, and that the pinions 4 and be alike, as'to their number of teeth, whereby the double differential gearing as a whole may be referred to as symmetrical.

The diflerential gears 5 and l have drivingly connected thereto, gears or pinions II and II, respectively, both of which are meshed with a gear connected to a power output element or load driving element II, which, in Fig. 1, is shown diagrammatically as a power output shaft.

The differential gears and H are respectively connected to shafts GI and G2 which. respectively, drive the rotors 2| and 2| of induction generators indicated generally at 22 and 2|.

While the construction of the generators 22 and 2| may be varied in the practice of the invention, I prefer to employ induction generators having the general construction Of alternating current squirrel cage motors, and in such case the rotors 2| and 2| would be squirrel cage rotors. The stators of the generators 22 and 2| having such construction comprise windings, which, when they are of motor construction and used as motors, are generally three phase windings: but .in the embodiment of Fig. 1, it is contemplated that each of the generators 22 and 2| shall have its stator windings energized with single phase alternating current. and to this end the stator winding of the generator 22 has the three parts 24, 25, and 2| thereof reconnected to dispose them in series, the windings 24 and 2| being connected together by a wire 21, the windings 25 and 2| by a wire 2|. and the wind- .4 contact 4| engageable with the tap points 42-42 as it rotates. A wire 4| connects the arm 4| with both wires and 8|. The wire |4 is connected to one end of the transformer winding at 41 and the wire 2| is connected to the other end of the transformer winding at 4|.

By this arrangement it will be apparent that when the contact 4| is on the midpoint of the autotransformer. potential will be supplied by the wires |4, |l, and 4| to the winding of the generator 2|, and by wires 2|, and 4| to the winding of the generator 22. and that these potentials will be equal; and that when the arm l| is rotated by its shaft 44 to other tap points of the transformer, the potential applied to one generator winding will be greater than that supplied to the other. To rotate the arm 4|, the shaft 44 may for convenience be provided with ahandle 4|.

The power supply motor may be an kind of a motor as hfisbeen referred to, but in the showing of Fig. 1 andflor convenience it is an alternating current induction motor connected by wires to a three phase alternating current supply main, of which the said wires and 4| may be two of the three mains, and a wire may be the third main.-

A line switch not shown may be provided as will be understood to connect the mains 4|, 4|, and BI to a source of three phase alternating current, but this has been omitted for simplicity, so that in Fig. l, the motor may be considered as energized and continuously running; and

ings 24 and 2| having external wires 2| and N connected thereto.

By a similar arrangement. the windings |l, |2, and of the generator 2| are connected in series and have external wires |4 and II connected thereto.

In the practice of the invention it is contemplated that the windings of the generators 22 and 2| will be energized respectively with single phase alternating current, and that the energization of both may be made equal, and that of one may be made greater than that of the other, and to this end, the following means is as is well known. the motor ll being a squirrel cage induction motor in this instance, will run at approximately constant speed with some slight and negligible variation depending upon the l1;;ower output which it delivers to the pin The operation of the apparatus of Fig. 1 will now be described. it being assumed that the arm 4| is at the start on the midtap of the transformer with the spider elements and driven in opposite directions by the motor II, the pinions 4-4 will supply equal torques at all times to their associated gears I and I, tending to drive them in the same direction as the spider and the pinions H of the spider I will likewise sup ply equal torques to the differential gears and "tending to drive them in the same direction as the spider 1.

Torque is thus transmitted to the differential ears and II causing them to drive the rotors 20 and 2| of the generators 22 and 2| and when the stators of these generators are equally energized as described, the torques developed at the gears and It will be equal and in opposite directions. Accordingly. the torques developed at the differential gears I and I will be equal to the torques at the gears and and therefore equal to each other, and in opposite directions; and these equal and opposite torques are transmitted to the gears and I1. but the latter both being meshed with the gear II on the output shaft it, and being in opposite directions, the gears It and II and the differential gears l and are prevented from rotating so that the load shaft l| remains at rest as a consequence of equal energization of the generators 22 and 2|.

As to the electrical loads of the generators 22 and 2|, it is known that if the stator of-an induction motor be ener ized with alternating current, and the rotor thereof be rotated at a sumciently hi h speed within the field produced by the stator energinilen, alternating 10 rotors 2.

cy of these units motors because of the t stators to the alternating current supply mains, is completely obliterated by the overpowering action of the motor I I. a

It would be possible of course as is well under- M by those skilled in the art to bring the and II of the generators up to full It may be further noted that with a double differential gearing of the type illustrated in Fig. I, when the gears l and II are rotating at the same speeds they will have a certain arithmetical sum of revolutions per minute: and this n arithmetical sum remains a constant as one gear I have found it to be afact that if an induction I motor be connected to commercial alternating current supply mains, through a transformer,

and driven above synchronous speed, it will act as a generator and supp current back to the supply mains through the transformer; regardless of the power factor of its supply mains: and I have concluded that the presence of the inductive transformer sets upthe two necessar phasedisplaced current components.

It will be observed that this principle is utilized 'in Fig. 1; and that whenthearmllis onthe mid-tap of this transformer, the two electrical loads of the generators 22 and II will be equal.

and that torque supplied to the gears I and II to drive them willbe equal, and as a consequence l! to move the contact ll to some other tap point of the transformer, say in the clockwise direction as viewed in the drawing, the electrical load developed by the generator I! will become greater and that developed by the generator II will become smaller, due to the greater stator energization of one and the lesser stator energizetion of the other, and as a consequence the equal torques at the gears t and I will become greater than the equal torques at the gears II and I, and the gear 8 will slow down due to the increased load or the generator I! connected to it and the gear I will speed up; and the gear It will supply greater torque to the gear It than does the gear I1, and the output shaft II will be rotated in a corresponding direction. Similarly, by moving the arm 43 in the other direction and causing the load of the generator-II to be greater than that of the generator 22, the load shaft II will be caused to rotate in the other direction. The speed of the load shaft II in rotating will be commensurable with the degree to which the two loads of the generators are unbalanced.

As mentioned above, it may be convenient in starting up the apparatus to put the arm I. on the mid-point of the transformer to energize both generators 22' and 2! equally. The motor II obviously will be or suilicient horsepower size to supply adequate power to the output shaft I9 and also to the generators, so that with the generators equally energised the rotors of the generators are compelled to come up to a speed is slowed down by increased electrical load and the other correspondingly speeds up.

In order that the rotors of the generators, for

example the rotor 20 of the generator 22, shall always be driven at a speed high enough to cause it to act as a generator, it is only necessary that it will have such a speed when its generator is given the maximum electrical load and is rotating at its minimum speed. This of course would be determined by gear ratios in the gearing for a given speed of the motor II, and if it should be desirable or necessary to this end, a step-up gear ratio would be provided in the line of the shafts GI and GI, for example in the place indicated by the rectangles I2 and 53 by which the rotors of the generators would always be driven faster than their driving gears 6 and III. A modification of this kind is shown in Fig. 1A, where gears I4 and N in the rectangle 52 are illustrated.

From the foregoing it will be seen that if the hand wheel I! is rotated to dispose the arm 43 at the midposition on the transformer, the load shaft or power output shaft I9 will remain at rest, and that upon rotating the hand wheel 49 in one direction, the load shaft will rotate in a corresponding direction, and upon rotating it in the opposite direction the load shaft will come to rest and then rotate in the opposite direction; and that the speed of the load shaft will correspond to the angular extent of rotation of the hand wheel 49 from its midpoint, the power input motor II rotating at all times at full or high emci ency speed.

The form of Fig. 2 may be considered as a modification of the form of Fig. 1. e differential gears t and III and the shafts GI and G2 have been shown as in Fig. 1 to identify this form with the form of Fig. 1, and it is therefore-believed unnecessary to illustrate in this figure the rest of the differential gearing.

In this form, generators 56 and 51 are shown, driven by the shafts GI and G2, and as indicated diagrammatically these generators may have the construction of three phase squirrel cage motors having three phase stators. There are three autotransiormers 5t, 59 and 60 for energizing the three phases of the stator of the generator 56,

and three autotransformers BI, 82, and 83 for energizing the three phase stator circuit of the generator 51.

The windings of the transformers 58, 59, and I are connected at one end by wires N, 85, and 00 respectively to the mains 61, it, and, "of a higherthan the synchronous speed which they 15 three phase alternating current supply system,

connection oftheir I and the otherends thereof are connected to a common point ID by wires II, I2, and 13.

The windings of the transformers I, 82, and

are connected at one end by wires II, 15, and 16 to the respective wires of the three phase system, and their other ends are connected to a com mon point 11 by wires I8, II, and ll.

As will therefore be apparent there is shown generally at II and I2 a pair of three phase autotransformers.

Each of the windings of the transformer al has tap connections "-83, over which concurrently move, three contact arms I4, II, and It; and the arms also make continuous contact with alrcuate contacts l1, l8, and 89 which are respectively con nected by wires 80, 0|, and 82 with the stator of the generator 56.

The transformer 82 has a similar arrangement of taps 91-43, arms 94, I5, and ti, and arcuate contacts 91, I, and 89, for energizing the stator of the generator 51 over wires Ill, Ill, and I02.

The three arms of the transformer II are connected by a shaft III! to a gear I, and the three arms of the transformer 82 are connected by a shaft ID! to a gear III. meshed with the gear IN, and one or the other of the gears, for example the gear I06, may be rotated by a hand wheel II".

In view of the more complete description of the form of Fig. 1, it is believed to be apparent that when each of the contact arms is on the midpoint of its associated autotransformer winding, the stators of the generators l8 and 51 will be equally energized with three phase alternating current. producing a rotary field therein of intermediate or given strength, and that when the hand wheel II" is rotated in one direction or the other, the potential supplied to the stator winding of one generator will be increased and that of the other decreased concurrently; and when the stator windings are equally energized, the electrical load or braking drag on the gears i and III will be equal, and when, one is energized more strongly than the other the braking drag of that on will be decreased over that of the other for the purposes described; and that to produce this generator action it is only necessary that the rotors Ill and "s ot the generators be driven above the speeds at which the magnetic fields of their stators rotate, and while this in general will be true when thegears i and II are driven as described for If'ig, 1, it may be assured by stepping up the speed of the generator rotors as indicated in Fig. 1A and as described for Fig. 1.

It is also believed to be apparent that the energizing wires 80, ll, and 92; and IIIII, III, and I I02; of the two generators by which they are energized from the supply mains 81, 68, and I, are also the wires 'over which the electrical load output of the generators is supplied back to the same mains.

The operation of Fig. 2. therefore. will be the same as, that of Fig. 1; andas to construction, it is the same as that of. Fig. 1 except that the stators of the generators are three phase stators and as a consequence are each supplied by a three phase transformer.

In Fig. 3 is illustrated a modification in which only one differential gearing, shown generally at IIII, i utilized, together with only one induction generator III, this form otherwise being generally similar to Fig. 1. The spider II2 of the differential gearing is rotatably driven by a pinion III on the shaft of the motor Ill. The pinions IIlI I! rotatably supported by the spider I f2 enamels the gear Iii being connected to the output shaft III, and the gear II'Ibeing connected-by a shaft GI to the rotor II. of the generator III.

The stator windings of the generator III are connected in series as was described for the form of Fig. 1, and an autotransformer I" is energised by wires HI and I22 across alternating current mains I23 and I24. Anarm I2I, rotatable about a pivot center or axis or shaft I2l, moves cm W connection points I21, etc., of the transformer winding. The wires I28 and I2! connected to the stator winding are connected respectively to the gm I and to one end of the transformer wind- E. With this arrangement when the arm I2! is rotated clockwise to the last tap connection point, I2'IA, there will be no potential on the stator supply wires I2B-I28, and as the arm is moved counterclockwise over the tap connections greater and greater potential is applied to these wires to energize the stator winding more and more strongly.

For convenience, in considering this form, the arm I25 may be considered as first in its most clockwise position, with the stator of the generator unenerglzed, and with the motor II 4 running at full speed. If there be any considerable load connected to the output shaft Ill, the rotor Ill of the generator will therefore rotate idly, and without generating any electrical load, and it will run at twice the speed of the spider I I2 and the shaft I I8 will remain at rest. As the arm I2! is moved counterclockwise over the tap points I21, energizing the field of the generator, torque will develop at the gear I I1, and an equal torque at the gear I-IB, since the torque at the spider H2 at all times divides equally between the gears through the pinions H5, and the shaft I II will rotate.

The output shaft III therefore may have its speed controlled by rotation of the arm I 2|,

. If the load on the output shaft III is an overhauling load, for example if it be connected to the winding drum of a hoist with a load thereon, then the load will be moving at maximum when the winding of the generator III is unenergized; and as the winding is energized more and more, it will cause the gear I II to slow down, and the gear I I! and the load shaft I II will slow down, that is to say, its overhauling speed will become less, and ultimately, at a certain field strength, will come to rest. By further increasing the energization of the generator field, the load shaft II! will begin to rotate in the reverse direction and at increasing speed as the generator stator is energized more strongly, and correspondingly will raise the hoist load.

Thus speeds of the output shaft Ill for nonoverhauling loads will have a range from zero or rest speed up to a maximum speed; and for overhauling loads will have a range of speed from a maximum speed in one direction, to zero or at rest speed, andto a maximum speed in the other direction.

' -In Fig. 4 is illustrated a form which may be considered as a modification of Fig. 3 and it is identified therewith by reproducing the gear III and the shaft GI. The generator, here Ill, is of former I32, comprising three individual transformers I38, I31, and Ill. One end of the winding of each of the individual transformers is are meshed with differential gears III andlI'I. connected by-wiresill, I, and Ill to the reon spectivemains Ill, land Illoiathreephase areconnectedtoacommonpoint'lllhywires Ill, Il'I,andIll.

Contact arms Ill, Ill, and III moveover tap connection points on the individual windings oi thetranstormerandmakeconstantcontactwith arcua'te contacts Ill, Ill, and Ill to which the wires Ill,'Ill, and Ill are respectively connected.

By concurrently rotating the arms Ill, Ill, and Ill by any suitable means, for example by rotatin: a shaft Illtowhich they are all connected.

the strength'ol the energlzation or the stator oi the generator Ill may be'varied from zero to a maximum for thepurposes described; and it is mam.

Ill respectively. and the inner ends or the windlegs are connected to acommon'wire ll and the outer'ends are connected to wires ll and ll.

believedthattheoperationwillotherwlsebeunderstood (mm the morecomplete descriptionol the forms particularly that 01' Fig. 3.

In the forms of Figs- 1 to 4. thevfl'lri oi the energisation or the generator stator, whether single phase or three phase. is elected by a contact rotatahly moving over tap connections oi an autotranstormer arrangement.

The variations in speed or the output shaft therefore will occur in small steps. In some cases. it may be desirable to make the variation gradual or continuous or without steps. .Al o, in some cases, for example when the apparatus or the control part thereot is installed in an explosive atmosphere. it may be desirable to eliminate all possibility of electric arcs o'r sparks which might ignite such atmosphere. By using the induction type or generator all sparks are eliminated thereat (which would not be the case it direct current generators having commutators were used),

and to make the apparatus and its control com pletely spark-proof. the tendency to are or spark at the taps'oi theautotranslormers'would have 'tobeeliminated." H I v For all or theaemd results; which may in some cases be wanteiL-the arrangementsshown diagrammatically in Figs. 5 and-6 are provided by which the variation or the voltage appliedto the generator stators may be eflected inductively.

These devices of Figs. 5 and-6 are here 'rei'erred' toasinductorabutasamatteroitechnicalprincipie they are in eiIect transformers, the significance'or which willpresently be explained.

Magnetic fill! produced by the-"Winding Ill ilowsto both polar portions Ill and Ill, and

when the rotary-element Ill is in the mid-position illustrated it induces a low potential in the windings Ill and I'll, and that induced between the wires ll-ll by the winding Ill is equal to that induced between the wires "-14 by the winding I'Il.

Upon rotating the rotary element Ill, say, clockwise, to more nearly align the leg Ill with the-polar portion Ill and move the leg I l l still further out of alignment with the polar'po'rtion Ill, the potential across wires that across the wires "-36 falls.

stituted iorthe same wires in Fig.1; then upon rotation of the hand wheel Ill of Fig. 5 to dili'ers ent positions, the apparatus at Fig. 1 would operate the same as it does, andes described, upon rotating the hand wheel ll of Fig. 1.

In Fig. 6 is illustrated diagrammatically another form or inductor, the construction oi" which is similar to'that 01' Fig. 5 as indicated by the same reference characters rorsomeor the parts; but the rotary element "here III has a winding on only one ot'thetwo legs Iflland I'Il', namely. a winding ill on theleg I'll, connected to wires Ill and Ill. In the position ofthe ro'-' taryelement I'II illustrated; little or no potential is induced in the winding-Ill, most or the flux from the winding 'ill flowing to the polar portion Ill; and upon rotating the rotaryelej ment III counterclockwise byjthe hand wheel" Ill, more and morenux flows to the polar portion Ill and more and more in the wires Ill and Ill.

II the. wiressill and Ill 0! Fig. 6 be substituted for the same wires in'l ig. 3, and the shaft Ill of Fig. 6 be turned by its hand wheel Ill; the appa-- ratusoi Fig.3 would then operate the same as i was described for'it upon turning its shai't I ll;

Referring tol'lg. 5,'there is shown at Ill, an

E-shaped core which maybe of laminated steel the central core portion I-l'I oi which has thereon a'winding Ill energized across alternating current ml! mains --Ill. Between the polar portions Ill and I" is a rotary or bri ing ele ment Ill, supported to rotate and be rotated in alternate directions in anysuitable manner, for

example by being moimted upon a shaft Ill and rotatable by a worm Ill-engaged with aworm' In the forms oi Figs. 2 and 4, each of the inductlon generators has a three phase field energized irom three phase mains through three autotransformers, all three transiorm'ers-beingadjustable by a common rotary'shait; It is believed that it will now beapparent withoutiurther expanding the specification and drawinghe'reoig that three such inductors as shown in Fig. 8,-

each energized from a diirerent phase of a three; ande ch-s pplying current phase supply system, to one oi. the phases of the'generator stator'winding oi Fig. 4, and all adjustableibya -common gear Ill on the shalt, theworm being rotatable by a hand wheel Ill. The worm and gear engagement holrkthe rotaryelement -I ll in positions to which it is mtll dvby the hand wheel Ill and prevents it trommovlng from such positions by magnetic attraction or thepolar portions Ill andjili.

' main in Fig.4. three or the rug. 6 inductors for-f 'nle'rom element: has tw legs in and Ill disposed at an angle to eachother; such that the rotary element Ill may havea rotated position in which neitherleg I" or Illis fully aligned with the polarportions Ill and Ill, and other positions in which one or'the other otthe legs is more nearly aligned with one oi the polar posi-' tions. 'Ilhe angle illustrated is approximately 90 but this particular angle is not Windings Ill and I'll areiprovided-on the legs Ill and il tuted tor the two sets of shaft. would produce the same variable field energiaation oi the generator .Ill of Fig. 4 as described as does the-transformer arrangement of Fig, 4; This substitution' would' comprise'substi the three autotransi'ormers of Fig. 4; and that it will also beapparent that two sets oi. three or the i6 inductors could in a manner he substias is well known and this current load by as- 4o rises and It the wires ll, ll, and ll oi Fig. 5 were subpotential isinduced 4v and 2' wllloperatethe v i1 trensiormer action is supplied through the transiormerstothe wlymains. Whentheso-called inductors oil'igJorl'ig. B'areutiliaedthesame actionoccursinasmuchasthoeeinductorsue transformers in electromagnetic induction principle.

Autotransiormers have been illustrated and described but it is believed that it will be understood that transformers oi the W having separate primary and secondary windings with tap connectionsonthesecondarrmaybesubstituted.

Hand wheels are illustrated and described for changing the output potentials oi the transformers and inductors. but this will be understood as notessentiakandthatanyoth'ermeansmarbe" substituted. including automatic means responding tosome quentitroriactorwhichistobeoontrolled or regulated by the output shaft oi the ton.

As to the diflerentiai gearings. for example those ofl'ig. Lit eflectssimpliiicetiontohavethe spider elements 8 and I rotate in opposite directicns, and to have the gears l-lrotate in opposite directions withreepectto the gears ll|.but

this is not essential. Any arrangement, which mayinsomecasesinclude motion reversing gears betweenthegenerators oil'imlandthediilerenl2 gisediromthesourceendsupplyingtrenatormed s epbasepotentialtotheseriesstatorwindfl.andprovidedwithmeanstoradiustabll varyingthetrenstcrmedpotential.

3.Inepowertranamission.two diflerential s a lnsaeachoomprisingthreeelemenmnamely: a spider element rotatahly supporting a pinion. endtwodiilerentialgeersmeshedwiththepinion; a motor driving bothspider elements: one diilerentialgearoteachgeeringbeingdrivlngly connectedtoapoweroutputelementztheother diflerential gearoieachgearingbeing I eonnectedrespectivelytotherotorsottwoinductialgearingsorbetweenthegcarsllendlloi.

rig.1endthediiierentialsearings,maybeutillise'd,elthoughitisdesirabletohavesuchgsar generator having the construction of a three phasesquirrelcsgemotorwithitsthreephase stator windings connected in series; a source of alternating potential; an induction potential transforming device energised from the source and supplying transformed single phase potential to the series stator windings. and provided with means for adiustably varying the transformed P tential. 1

2. In a power transmission. a diiierentiai gearin comprising three rotatable elements, namely:

a spider element rotatably supporting a pinion and two diilerential gears meshed with the pinion; oneotsaidthreeelementsbeingdrivenbya motor; another 01' said elements being drivingiy connected to a power output element: end the third or said elements being drivinaly connected to the rotor of an induction generator having the construction of a three phase squirrel cage motor with its three phase stator windings connected in series; a source of alternating potential: en

40 causethatsuppliedtocnetobe tion generators each having a stator winding: a

potential transiormedpotentialtocause pliedtoboths'tatorwindings connected windings: and means to sdiustebly varythepotentialmwii dbrseid transiwmins 6. In a powertrensmission, a diilerential gearing comprising three elements namely: a spider element rotatably driven by a motor, and rotatably supporting a pinion. and two diiterential gears both meshed with the pinion; one dinerential gear being drivingly connected to a power output element;.the other diflerential gear being drivingly connected to the rotor of an induction generator having the construction oi a polyphase-stator induction motor with the polyphase stator windings connected in series; a source of alternating potential; an induction potential transforming device energised (mm the source and supplying transformed single phase poteninduction potential transforming device ener- 75 tied to the series stator windings; and provided 13. with means for adiustably varying the, transformed potential.

.7. In a power transmission. a differential gearing comprising three rotatable elements, namely:

a spider element rotatably supporting a pinion and two diil'erential gears-meshed with the pinion; one of said'three elements being driven by a motor; another of said elements being drivingly connected to a power output element; and the third of said elements being drivingly connected to the rotor of an induction generator having the construction of a poly-phase-stator induction motor with the polyphase stator windings the source and supplying transformed potential to the stator windings of the generators: and provided with mans for adjilstablx varying the transformed potential to cause the potential sup- ,pliedtobothstatorwindingstobeequalandto connected in series; a source of alternating potential; an induction potential transforming device energized from the source and supplying transformed single phase potential to the series stator windings. and provided with means for adiustably varying the transformed potential.

8. In a power on, a differential gearing comprising three elements namely: a spider element rotatably driven by a motor. and rotatably supporting a pinion. and two differential gears both meshed with the pinion; one diflerential gear being drivingly connected to a power output element; the other differential gear being drivingly connected to the rotor of an induction generator having the construction of a polyphase squirrel cage induction motor with the polyphase stator windings connected in series; a source of alternating potential; an induction potential transforming device energized from the source and suppmng transformed single phase potential to the series stator windings, and provided with means for adjustably varying the transformed potential.

9. In a power transmission, a diiferential gearing comprising three rotatable elements, namely: a spider element rotatably supporting a pinion and two differential gears meshed with the pinion; one ot said three elements being driven by a motor; another of said elements being drivingly connected to a power output element; and the third of said elements being drivingly connected to the rotor of an induction generator having the construction of a polyphase squirrel cage induction motor with the polyphase stator windings connected in series; a source of alternating potential; an induction potential transforming device energized from the source and supplying transformed single phase potential to the series stator windings, and provided with means for adjustably varying the transformed potential.

10. In a power transmission, two diiferential gearings each comprising three elements. namely: a spider element rotatably supporting a pinion, and two differential gears meshed withthe pinion; a motor driving one of the elements of both gearings; another element of each gearing being drivingly connected to a power output elemotor supplying power to the transmission; a

ment; the other element of each gearing being drivingly connected respectively to the rotors of two induction generators each having a stator winding; a source of alternating potential; an

induction potential transforming device energized from the source and supplying transformed 11. In a power transmission, two diflerential gearings each comprising three elements, namely: a spider element rotatably supporting a pinion; and two diilerential gears meshedwlth'the pincause that supplied to one to be greater than that supplied to the other. I

12. In a power transmission, a dliferential gearing comprising three elements namely; a spider element rotatably driven by a motor. and rotatably supporting a pinion. and two differential gears both meshed with the pinion; one

' differential gear being drivingly connected to a power out put element; the other differential gear being drivingly connected to the rotor of an induction generator having an electrically energizable stator field winding; a source of alternating potential; an induction potential transforming device energized from the source and having a circuit over which it supplies alternating current at transformed potential to energize the stator field winding and over which alternating current generator load is supplied from the stator field winding back to the source when the rotor is driven above synchronous speed of the stator field winding and means to adiustably vary the transformed potential to vary the generator current load.

13. In a power transmission, a diflerential gearing comprising three rotatable elements, namely: a spider element rotatably supporting a pinion and two difierential gears meshed with the pinion; one of said three elements being driven by a motor; another of said elements being drivingly connected to a power output element; and the third of said elements being drivingly connected to the rotor of an induction generator having an electrically energizable stator field winding; a source of alternating potential; an induction potential transforming device energized from the source and having a circuit over which it supplies alternating current at transiorm'ed potential to energize the stator field winding and over which alternating current generator load is supplied from the stator field winding back to the source when the rotor is driven above synchronous speed of the stator field winding; and means to adjustably vary the transformed potential to vary the generator current load.

14. A power supplying unitcomprising: a mechanical transmission; a continuously running power take oif from the transmission; an alternating current induction generator having a rotor, and a stator field winding and an exciting circuit for the winding; the rotor being driven by the transmission; a source of alternating potential; induction potential transforming means supplying alternating current at transformed potential from the source over the exciting circuit to energize the stator field winding to cause the generator to develop electrical load in the stator field winding; and the said circuit conducting the generated current load back to the source through the transforming means when the rotor is driven above synchronous speed of the stator field winding; the transmission being responsive to variations of generator load to vary the trans- .15 16 misaiotiiiupower output; end means to vary title I'ORIIGN PATENTS poten supplied by the transforming means 0 m my z ma mmov' 042,766 moo m 9: 1923 REFERENCES CITED arm REFERENCES The iollowing references are oi. record in the Lawrence: "Principles of A. C. Machinery," tile oi this potent: second edition, 1921, mes 497 to 504, McGraw- UNITED STATES m'mms m 9"- Number Name Date 729,199 Meyer May 28, 1903- 1,221,891 Thullen Apr. 3, 19-1! 1,867,718 Connell my 1, 1928 

